Mass air Flow Sensor Shuts down ignition
 

Baby steps. Last week I hit 1000 rpm, today i hit 1500 rpm.

Trying to start my car the ignition is shut off when the mass air flow sensor is plugged in. Now, when I plug in the mass airflow sensor it is easy to tell that the gas pressure increases.... but it does me no good because I can't get ignition with it plugged in. My question is why would the mass airflow sensor that appears to be working be shutting off my ignition?


In other notes, one of my primary injectors sounds stuck when the mass air flow sensor is plugged in. I am going to try switching primaries w/ secondaries along with cleaning the plugs again to try to get it going this week.




SAR

What year is your RX7?

you should probally try to check the wires all the way back to make sure there is no short going on.

my car year: 1887
 

My rx7 is a 1987 se (NA). It sat for 10 years until I bought it and am trying my best to get the thing going.

Last week it ran on starting fluid (i like ether :D ) to 1000 rpms...

This last week I cleaned up the upper intake maifold, throttle body, egr an lim pipes and really cleaned them out... including getting the secondary throttle plates to be able to move again. Previousley I had to replace the fuel pump after emptying the tank and cleaning that for a week.,

So now it is running on gas... not sure how good the gas is getting sprayed by the injectors (which I cleaned and triggered)., but it hit 1500rpm until it stopped tonight, apparently the plugs are flooded with oil/gas. Tomorrow I will clean those up.

Strange as it sounds, you're not the first to have the problem of the AFM killing the spark when plugged in. I don't think anybody yet has fully explained why this happens, my best guess is that the ECU kills the engine when an AFM input triggers a "danger" mode. Which input, the door switch, the door position, the 5v ref signal, the temp sensor, I don't know.

Have you read out the AFM? The FSM has all the procedures to accomplish this in section 4A, page 53...

If that all looks good, the next thing I would check is the AFM door position input signal at the ECU (pin 2E), and the AFM intake air temp sensor input (pin 2J)...2J can be read with just key on, and 2E can be read with a "helper" slowly pushing the door open, key on, if you can't keep her running...

The AFM could run a nasty failsafe. AFM dies, and it throws the accident failsafe to cut off gas. It makes sense really underterms of failsafes.

If this wasn't in place, the AFM would go bad and the accident failsafe may not work-- hence fire if you're unlucky.

Try hotwiring the gas pump to rule out the AFM's failsafe.

I had the same problem, in my opinion the afm failsafe doesnt just effect the fuel pump. I had a connector break inside the afm and it would start and run without it plugged in but when i plugged it in it wouldnt start. Then i fixed the broken connector and it worked fine. My fuel pump was hotwired.

You guys are ignoring one basic EFI concept. The AFM (and any other sensor) does not do anything other than send a couple of signals to the ECU. The ECU makes all the decisions and operates all the output devices. If the ECU gets receives incorrect signals from the AFM, it will do incorrect things.

The only exception to this is the AFM's safety switch (which at zero airflow turns off the fuel via the circuit opening relay), which has no connection to the ECU at all.

The AFM needs to be checked as per the FSM instructions like Wayne said.

****Trying to start my car the ignition is shut off when the mass air flow sensor is plugged in*****

How did you determine the ignition is shut off????????????

Try this: unplug the fuel pump AT the fuel pump connector. It's under the rug on the aft side of the left strut tower.

Now with that disconnected and the afm plugged in, start the car using starter fluid. If it starts.....it ain't the ignition being cut by the afm (not a likely scenario). NOTE: Use common sense and never KEEP an engine running with starter fluid. Just use it to start an engine. To know why, just go to your lawnmower engine and start it. Now spray starter fluid in the mowers intake. You WILL now know what KNOCK is. Just FYI.

I think the engine is being flooded, not ignition cut. (and or you have a bad rotor).

****** I Know that the ignition is turned off due to lack of tach... and secondly due to the screwdriver test*******

I believe that the engine is being flooded now also, as I can only reach 500-1500 rpm with the afm off.... I get no tach w/ the afm connected, and as tach is based off of the coils/ignitors I have discovered that this is the quick way to discover no spark.

About the ether... yeah, I know its a bad idea to have to use it to hit higher rpm.....

No tach just means no trailing spark, which the car can run without. In fact, the ECU will shut down the trailing side and throw a code, if it detects something wrong, leaving the leading alone...

That's an interesting question- just what exactly WILL trigger the ECU to shut down the trailing system? Any ideas, NZ?

Maybe if the ECU loses its select signal processing ability, hmm???

I can't think of any good reason why the ECU would shut down only the trailing plugs. I'm sure it'd be all or nothing.

I can't think of any good reason why the ECU would shut down only the trailing plugs. I'm sure it'd be all or nothing.****

May not be rational, but I'm sure I've seen that before and posted that in the past on this forum. It happened when there was a battery problem. I remember it happened just after jumping the car off another battery. I went for a drive and noticed the Tach not working. After stopping and turning the engine off, then starting again all worked wiell again. I remember that happening at least twice in the past. Maybe it was just a stuck tach.....don't think so.

As far as this thread goes......SAR, .since you know a quite a bit about the car, I still recommend removing the lead plug wires and laying them on the fender. Then remove the cas with the connector still on, and twirling the cas lower gear. The plugs should spark big time (key to ON). Try it with and without the afm plugged in. That ought to telll you something. It takes but ten minutes to try out.